Ruby on Rails API for beginner json response - ruby-on-rails

Question

I am new to ruby on rails. I apologize early if this question might be dumb... but I can't figure this out and the tutorials I've seen is making this simple task confusing. Or I am just not understanding what I am missing or what to do... if a step by step tutorial may help, thanks!
My task to make a rails api that you can pass JSON to via postman/DH.
The payload will be {"value": "foo"}. A '200 (OK)' Response with payload of {"value":"bar"}
No database needed, just a controller that takes in a payload and gives back a response.
This is what I do know...
What I do know is how to create a rails api by "rails new testrails --api"
Then going to my 'gemfile' and installing some kind of json to gems.
Then... I mess with the 'route.rb' file in config and the controller in'apps'.
I get lost here on what I need to do with the route file and controller...
What ever steps come next.

Answer 1

Step 1: install Rails 5
$ gem install rails
Step 2: create an API-only Rails application
$ rails new my_app --api
Step 3: integrate rack-cors
Add gem 'rack-cors' at the bottom of your $RAILS_ROOT/Gemfile ($RAILS_ROOT stands for the root directory of your rails app), then
$ bundle install
Then add these lines to your $RAILS_ROOT/config/application.rb, inside the class definition
config.middleware.insert_before 0, Rack::Cors do
allow do
origins '*'
resource '*', :headers => :any, :methods => [:get, :post, :patch, :put, :delete, :options]
end
end
Step 4: generate a controller
$ rails g controller foo
Add an action to the FooController (in file $RAILS_ROOT/controllers/foo_controller.rb)
def create
foo = params[:foo]
# Do whatever you want with foo
render json: {value: 'bar'}
end
Step 5: add a route
Modify the file $RAILS_ROOT/config/routes.rb, add
post '/foo' => 'foo#index'
in the block
Step 6: start rails server
$ rails s
That's all. Now you can send POST requests to http://localhost:3000/foo and see what happens.